Physiological changes in lupine plants in response to salt stress and nitric oxide signal

Elevated concentrations of salt induce ionic and osmotic stress, hindering plant development and growth through impairing various crucial metabolic functions. The current study was conducted to fathom how nitric oxide (NO) induces salinity stress tolerance in Lupinus termis L. plants. Varying concentrations of sodium chloride (0.0, 75 and 150 mM) were introduced to plants with/without supplementation of NO (in the form of sodium nitroprusside, 0.4 and 0.6 mM) to detect the associated metabolomic changes. Growth parameters, oxidative markers (lipid peroxidation, H2O2, and electrolyte leakage), photosynthetic pigments, phytohormonal content, certain osmoprotectants (organic acids contents, proline, soluble sugars, and polysaccharides), and mineral ions (Na+, Ca2+, K+, Mg2+) were determined in both shoots and roots. NO exogenous application significantly diminished the salinity-induced oxidative stress and alleviated salt's inhibitory effect on lupine growth and photosynthetic pigment content. The most effective SNP (sodium nitroprusside) concentration in boosting salt stress tolerance in lupine was 0.4 mM. This could be correlated to the found upregulation of osmoprotectant molecules including soluble sugars, polysaccharides, and organic acids, namely malic, succinic, formic, acetic, and butyric acids, besides increased endogenous hormones level. In addition to the increased divalent cations (Ca2+ and Mg2+) content, reduced Na+ intake, and increased K+ influx in lupine plants supplemented with 0.4 mM SNP was evident.